Seismic Design of WESSeismic Design of WES--BRB and BRB and G t C tiG t C tiGusset ConnectionsGusset Connections

林保均 / Pao-Chun LinAssistant ResearcherAssistant Researcher

National Center for Research on Earthquake EngineeringM.S. / Civil Engineering Department, National Taiwan University

Using WESUsing WES--BRBs for An Improved Seismic Resisting PerformanceBRBs for An Improved Seismic Resisting Performance of Buildingsof BuildingsAuckland, Wellington and Christchurch, New Auckland, Wellington and Christchurch, New ZealandZealand

Nov. Nov. 1212--14, 14, 20132013

Seismic design of BRBFSeismic design of BRBFDesign base shear force VdesignBRB axial force = 0 9PyBRB axial force = 0.9Py

0.9Py

0.9Pyy

Base shear

0.9Py

Vdesign

VdesignStory drift

Seismic design of BRBFSeismic design of BRBFDesign base shear force VdesignBRB axial force = 0 9Py

PmaxPmax

BRB axial force = 0.9Py

Max base shear force V

PP

Max. base shear force VmaxBRB axial force = Pmax

The gusset plates are required to sustain the PmaxPmax

Base shear

The gusset plates are required to sustain the BRB max. axial force Pmax

PmaxVmax Pmax

Vdesign

VmaxStory drift

Brace Brace On On DemandDemand browser browser Brace Brace On On DemandDemand browser browser Design requirement

space strength stiffnessspace strength stiffness

Design results

1 WES-BRB1.WES-BRB2.Gusset 3 Welding3.Welding4.DCR checks

http://bod.ncree.org.tw

User guide for BOD usersUser guide for BOD usershttp://bod.ncree.org.tw

DemanCa

=p

DCR dacity

7 categories of limit state Load and Resistance Factor

Capacity

Load and Resistance Factor Design

Specification for Structural Steel pBuildings (AISC 360-10)

Seismic Provision for Structural Steel Buildings (AISC 341-10)

P.C. Lin, K.C. Tsai, K.J. Wang, Y.J. Yu, C.Y. Wei, A.C. Wu, C.Y. Tsai, C.H. Lin, J.C. Chen, A.H. Shellenberg, S.A.Mahin C W Roeder Seismic design and hybrid tests of a full-scale three-story buckling-restrained frameMahin, C.W. Roeder, Seismic design and hybrid tests of a full-scale three-story buckling-restrained frameusing welded end connections and thin profile, Earthquake and Structural Dynamics, 2012, 41:1001-1020P.C. Lin, K.C. Tsai, A.C. Wu and M.C. Chuang, Seismic design and test of gusset connections for buckling-restrained braced frames, Earthquake Engineering and Structural Dynamics, 2013, eqe. 2360

OutlineOutline IntroductionIntroduction

S i i d i f BRBFS i i d i f BRBFSeismic design of BRBFSeismic design of BRBF Design of BRB and gusset connectionDesign of BRB and gusset connectiong gg g

WESWES--BRB component designBRB component designUniform force method (UFM)Uniform force method (UFM)( )( )Generalized uniform force method (GUFM)Generalized uniform force method (GUFM)Frame action effectsFrame action effects

Test and analysis on BRBFTest and analysis on BRBFLargeLarge--scale Test and FEM analysisscale Test and FEM analysisLargeLarge--scale Test and FEM analysisscale Test and FEM analysis

ConclusionsConclusions

DCRDCR--11 // Steel casing bucklingSteel casing bucklingTh t l i t t The steel casing must prevent the BRB from flexural buckling.

IIscsc : : moment of inertia moment of inertia provided by steel provided by steel

iiscL

casingcasing

N)

y h yR P

maxPDemand:Demand:Fo

rce

(kN

y yR P

Capacity:Capacity:

2

scEIP

Axi

al F

R PCapacity:Capacity: 2esc

PL

Axial Displacement (mm)y h yR P

DCRDCR--22 // Joint region yielding Joint region yielding

The BRB joint sectionjA :: joint section crossjoint section cross--sectional areasectional area The BRB joint section

must sustain the maximum brace max /P

sectional areasectional area

tensile force and remain elastic.

max /P

max /PDemand:Demand:

Capacity:Capacity: y y jF R A 0.90

y y j

(AISC 360 10 D2)(AISC 360-10, D2)

DCRDCR--33 // Joint region buckling Joint region buckling Th BRB j i t ti f t i d l th f W P The BRB joint section of unrestrained length from W.P.

to the steel casing end must sustain the maximum brace force and remain elastic

maxPbrace force and remain elastic.

maxPDemand:Demand:

Capacity:Capacity: 0.90bL

2

2min ,yy y j

EIF R A

b

24

y y jbL

(AISC 360-10 E1)work pointwork point

(W P )(W P ) 0.02 cL

(AISC 360 10, E1)(W.P.)(W.P.)

BRB endBRB end--toto--gusset space requirementsgusset space requirements8TBRBBRB dd fill ld l hfill ld l h LL

max0.707 0.6 4w exx w jL DT F P

0.750.8w cT t BRBBRB endend--toto--gusset fillet weld length gusset fillet weld length LLww

Slab tick.Slab tick. ttss (150mm)(150mm) BRB end clearance BRB end clearance

i ti trequirements:requirements:to slabto slab: : 50mm50mmto beam faceto beam face:: 75mm75mm

LLww

to beam faceto beam face: : 75mm75mmto column faceto column face:: 75mm75mm

50mm50mm clearances at theclearances at theLLDDjj

50mm50mm clearances at the clearances at the gusset plate edgesgusset plate edges

Configure the gusset plate Configure the gusset plate

LLvv

g g pg g plength length LLhh and height and height LLvv

LLhh

DCRDCR--44 // Gusset plate block shear failure Gusset plate block shear failure S l t i t t l t thi k t d L Select appropriate gusset plate thickness tg and Lwso

the gusset must sustain the maximum brace tensile force and avoid the block shear failure

max /PDemand:Demand:force and avoid the block shear failure.

Capacity:Capacity: 0.75

, ,0.6

0 6

n u g nv u g ntP F A F A

F A F AwL

, ,0.6 y g gv u g ntF A F A

jD (AISC 360-10, J4)

gt nt j gA A D t

2gv nv w gA A L ttensile areashear area

gt :: gusset thicknessgusset thicknessgt nt j gt

DCRDCR--55 // Gusset plate yielding Gusset plate yielding Th t l t t t i th i b

/PD dD d/P

The gusset plate must sustain the maximum brace tensile force and remain elastic.

max /PDemand:Demand:max /P

TheThe yieldingyielding capacitycapacity ofof thetheTheThe yieldingyielding capacitycapacity ofof thetheWhitmoreWhitmore sectionsection regionregion onon thethegussetgusset plateplate isis adoptedadopted asas thethecapacitycapacity

Capacity:Capacity: 0 90

ocapacitycapacity.. (Whitmore RE, 1952)

Capacity:Capacity: 0.90,y g e gF B tBBee

(AISC 360-10, D2)

Fy,g: gusset plate material yield strength gusset plate material yield strength

DCRDCR--66 // Gusset plate bucklingGusset plate buckling Th t l t t t i th i b f

P

The gusset plate must sustain the maximum brace forceand avoid gusset plate flexural buckling.

maxPDemand:Demand:maxP1 2 3

rL L L

L

ThTh b klib kli t tht th ff thth WhitWhit3r

Gusset buckling lengthGusset buckling lengthTheThe bucklingbuckling strengthstrength ofof thethe WhitmoreWhitmoresectionsection regionregion andand thethe averageaverage ofofcriticalcritical lengthlength onon thethe gussetgusset plateplate isis

C iC i

o

L3(Thornton WA, 1984)

adoptedadopted asas thethe capacitycapacity..

Capacity:Capacity: 0.90L1

L2 ,cr g e gF B tL2

2

,0.658 , 1.50 877

cy g c

cr g

FF

,2 ,

0.877 , 1.5cr gy g c

cF

WhitmoreWhitmore section regionsection region e gB t

(AISC 360-10, E1)

BRB axial force BRB axial force -- Uniform Force Method (UFM)Uniform Force Method (UFM)(Thornton, 1991)(Thornton, 1991)••Adopted by AISCAdopted by AISC••Si l d i h f dSi l d i h f d

c

••Simple and straightforwardSimple and straightforward••Irregular or undesirable Irregular or undesirable gusset shapegusset shape

c

gc

φφgusset shapegusset shape

gbgcg

maxg

gc

βV P

bbgb

g

maxgc

c

reH P maxgc

b

H PreV P 2 2

β maxb

gbV Prα

b g c gr e β e α

e β max

ggb

αH P

r

tan b g

c g

e βφ

e α

BRB axial force BRB axial force -- Generalized Uniform Force MethodGeneralized Uniform Force Method(UFM)(UFM)

(Muir, 2008)••Designers can configure Designers can configure

φφ(UFM)(UFM)

g gg gthe gusset in any shapethe gusset in any shape••Compute the gusset Compute the gusset p gp ginterface forces according interface forces according to the gusset shapeto the gusset shape

cmax

max

sincuc

b

e φH Pe β

c

Vuc

2β

max

cos sinb

b b cub

β

e e β φ e φV P

α e β

bHub

VubHuc2β

max cosb

ub uc

α e βH P φ H

bb2α max sinuc ubV P φ V

Frame action effectsFrame action effects

LvLv

LhLh

inflection point

L/2L/2

Frame action effectsFrame action effects

Joint Joint closescloses

VbeamVbeaminflection

point

L/2L/2

Frame action effectsFrame action effects

Joint Joint opensopens

VbeamVbeam

inflection point

L/2L/2

Frame action effect Frame action effect -- equivalent strut modelequivalent strut model(Lee, 2002)• The equivalent strut axial force

represents the frame action forceLgS

Nrepresents the frame action force•Compute the Vbeamby assuming the beam plastic hinges form at Lh Lh

S

p,beam Vbeam

gusset tipsinflection pointL/2 2 y b p beamR M

L

(Kasai, et. al, 2008)(Chou, et. al, 2011)

, ,

,y b p beam

beam p beamh

V VL L

0 3 0 18d L V L L

SNLg

Lv

Lv

0.3 0.184 0.3 0.18

b h b h

bb h b v

d L V L LS I d L d L

t

Vbp,beam

SLh Lh

eam

0.3 0.184

g

b v b h

t

d L V L LN Iinflection

pointL/2

4 0.3 0.18b

b h b vg

N I d L d Lt

Frame action effects Frame action effects -- FEM analysisFEM analysisBRBBRB in tension in tension

BeamBeam--toto--column joint closescolumn joint closesG t l t i dG t l t i d

Mp,beam

Gusset plate is compressedGusset plate is compressed

Mp,beam

MMp,beam Mp,beamMp,beam

von Mises stress (GPa)Gusset plate is tensionedGusset plate is tensioned

BRBBRB in compression in compression BeamBeam toto column joint openscolumn joint opens

The beam plastic hinges form at inter-story drift of 0.016 rad.BeamBeam--toto--column joint openscolumn joint opens

Combined effects: Combined effects: BRBBRB + + frame action effectsframe action effectsc

c

uc

uc

bb

ubub

Joint opensJoint opens

b

uc c

ub

ubub

ucb

b

c

Joint closesJoint closesub b

frame action forces + BRB axial forceequivalent strut model + UFM / GUFM

c uc c ucV =V +N H =S - Hequivalent strut model + UFM / GUFM

Gusset interface b ub b ubV =N - V H =H +Sforce demands

Th t t th t t i th bi dDCRDCR--77--1, DCR1, DCR--77--44 // GussetGusset interface strengthinterface strength The gusset strength must sustain the combined von

Mises stress resulting from brace maximum axial force and frame actionand frame action.

DemandDemand::(beam)(beam)

VmaxP DemandDemand::

(column)(column)

Hc

Vc 2 2

3c cH VL t L t

2 2

3b b

h g h g

V HL t L t

LL cv g v gL t L t

h g h gL t L t LLvv

DCRDCR--77--11 DCRDCR--77--44

Capacity:Capacity: 1.00

HbVb

LLhh

,y gFhh

DCRDCR--77--2, DCR2, DCR--77--55 // GussetGusset interface strengthinterface strength Th t t th t t i th i l The gusset strength must sustain the maximum normal

stress resulting from brace maximum axial force and frame action and avoid the tensile rupture failureframe action, and avoid the tensile rupture failure.

D dD d D dD dmaxP

HV

DemandDemand::(beam)(beam)

DemandDemand::(column)(column)

HcLL

c

v g

HL t

b

h g

VL t

DCRDCR--77--22 DCRDCR--77--55cLLvv

v g

Capacity:Capacity: 0.75 u gF

Vb

LLhh ,u gLLhh

,u gF : gusset material tensile rupture strength: gusset material tensile rupture strength (AISC 360-10, J4)

DCRDCR--77--3, DCR3, DCR--77--66 // GussetGusset interface strengthinterface strength Th t t th t t i th i h The gusset strength must sustain the maximum shear

stress resulting from brace maximum axial force and frame action and avoid the shear rupture failureframe action, and avoid the shear rupture failure.

D dD d D dD dP

V VH

DemandDemand::(beam)(beam)

DemandDemand::(column)(column)

maxP

LL

Vc c

v g

VL t

b

h g

HL t

DCRDCR--77--33 DCRDCR--77--66LLvv

Capacity:Capacity: 0.75 0.6 u gFLLhh

Hb

,u gLLhh

(AISC 360-10, J4)

BRBFBRBF beam designbeam design The beam must be designed The beam must be designed

to sustain the axial force to sustain the axial force resulting from the BRBresulting from the BRBresulting from the BRB.resulting from the BRB.

The beam with suitable The beam with suitable flexural capacity (flexural capacity (MM bb ) can) canflexural capacity (flexural capacity (MMp,beamp,beam) can ) can reduce the force demands reduce the force demands from frame action effect.from frame action effect.

SNLg

L

Lv

, ,y beam p beamR MV V

2

Vbp,beam

SLh Lh

Lv

,beam p beamh

V VL L

Vbeam

inflection point

L/2

300

LargeLarge--scale BRBF testsscale BRBF tests

0100200300

3F displacementroof disp. history

300-300-200-100

Test 1, hybrid test, PGA = 530 gal

0100200300

3F displacementroof disp. history

-300-200-100

0

Test 2, hybrid test, PGA = 530 gal

100200300

3F displacement-300

roof disp. history

-200-100

0

Test 3 Cyclic loading test-300200

0 1 2 3 4 5 6 7 8 9 1011121314151617181920

Test 3, Cyclic loading test

earthquake time (sec)

0.20.40.6

nd ion

(g)

LA03 PGA = 0.53gLargeLarge--scale BRBF scale BRBF hybridhybrid ttestsests

-0.6-0.4-0.2

00.2

grou

nac

cele

ratihybrid hybrid ttestsests

LA03 (phase2)20003000

LA03 (phase1)

2 4 6 8 10 12 14 16 18 20 22time (sec)

0.60 2 4 6 8 10 12 14 16 18 20

(time)

530gal

010002000 530gal

2nd Story-3000-2000-1000

2nd Story

3000hear

(kN

)LA03 (phase2)530gal

100020003000 LA03 (phase1)

530gal St

ory

Sh

1st Story-2000-1000

0

ExperimentPISA3D1st Story

-4 -2 0 2 4

1 Story

Inter-Story Drift (% rad.)-4 -2 0 2 4

-3000 OpenSEES1st Story

Gusset interface welding failuresGusset interface welding failures Fractured at Hybrid Test 2Fractured at Hybrid Test 2interinter--story drift: 0.038 rad.story drift: 0.038 rad.

Fractured at Cyclic loading testFractured at Cyclic loading testFractured at Cyclic loading testFractured at Cyclic loading testinterinter--story drift: 0.039 rad.story drift: 0.039 rad.

Gusset plate edge stiffener Gusset plate edge stiffener -- increase the outincrease the out--ofof--plane stabilityplane stability

(GPa)0.038 inter0.038 inter--story drift story drift

Reduce the stress concentration at gusset tipsReduce the stress concentration at gusset tips

FEM analytical results FEM analytical results (von (von MisesMises stress)stress)(GPa)(GPa)(GPa)(GPa)(GPa)(GPa)

360 0.38 0.39 0.4 0.41 0.42 0.43( )

without stiffener1 5t

0.38 0.39 0.4 0.41 0.42 0.43( )

without stiffener1 5t

0.38 0.39 0.4 0.41 0.42 0.43( )

without stiffener1 5t

0.38 0.39 0.4 0.41 0.42 0.43( )

without stiffener1 5t

0.38 0.39 0.4 0.41 0.42 0.43( )

without stiffener1 5t

0.38 0.39 0.4 0.41 0.42 0.43( )

without stiffener1 5t

gusset thick. (tg) = 15 mm

360 mm

(22 5 )1.5tg

2.5tg

3.5tg

4 5t

1.5tg

2.5tg

3.5tg

4 5t

1.5tg

2.5tg

3.5tg

4 5t

1.5tg

2.5tg

3.5tg

4 5t

1.5tg

2.5tg

3.5tg

4 5t

1.5tg

2.5tg

3.5tg

4 5t

g ( g)

mm

(22.5 mm)(37.5 mm)(52.5 mm)(67 5 mm)4.5tg4.5tg4.5tg4.5tg4.5tg

Stiffener thick.t 15mm

4.5tg

250 (67.5 mm)

0 38 0 39 0 4 0 41 0 42 0 430 38 0 39 0 4 0 41 0 42 0 430 38 0 39 0 4 0 41 0 42 0 430 38 0 39 0 4 0 41 0 42 0 430 38 0 39 0 4 0 41 0 42 0 43

tsf = 15mm

0 38 0 39 0 4 0 41 0 42 0 430.38 0.39 0.4 0.41 0.42 0.430.38 0.39 0.4 0.41 0.42 0.430.38 0.39 0.4 0.41 0.42 0.430.38 0.39 0.4 0.41 0.42 0.430.38 0.39 0.4 0.41 0.42 0.430.38 0.39 0.4 0.41 0.42 0.43

Stiffener width wsf 1.5tg 3.5tg2.5tg 4.5tg

Minimum required stiffener cross-sectional area 2.5tg x tg

DCR and design checksDCR and design checks1.1. BRB componentBRB component

DCRDCR--11 / / steel casing bucklingsteel casing bucklingDCRDCR 22 // j i t i i ldij i t i i ldiDCRDCR--2 2 / / joint region yieldingjoint region yieldingDCRDCR--3 3 / / joint region bucklingjoint region buckling

2.2. BRBBRB endend--toto--gusset connectiongusset connectionDCRDCR--4 4 // gusset plate block shear failuregusset plate block shear failureDCRDCR 55 // t l t i ldit l t i ldiDCRDCR--5 5 // gusset plate yieldinggusset plate yieldingDCRDCR--6 6 // gusset plate bucklinggusset plate buckling

3.3. GussetGusset--toto--beam and column interfacesbeam and column interfacesDCRDCR--77--11 // gussetgusset--toto--beam von beam von MisesMises yield criterion yield criterion DCRDCR 77 22 // gussetgusset toto beam tensile fracturebeam tensile fractureDCRDCR--77--22 // gussetgusset--toto--beam tensile fracturebeam tensile fractureDCRDCR--77--33 // gussetgusset--toto--beam shear fracturebeam shear fractureDCRDCR--77--44 // gussetgusset--toto--column voncolumn von MisesMises yield criterionyield criterionDCRDCR 77 44 // gussetgusset toto column von column von MisesMises yield criterionyield criterionDCRDCR--77--55 // gussetgusset--toto--column tensile fracturecolumn tensile fractureDCRDCR--77--66 // gussetgusset--toto--column shear fracturecolumn shear fracture

Design checks of diagonal BRBFDesign checks of diagonal BRBF

Gusset to beam, von Mises yield criterionDCR-7-1 upperDCR 7 2 upper

7 Categories of limit state

DCR-6 upperGusset plate buckling

DCR-7-2 upperGusset to beam, tensile rupture

Gusset to beam, shear ruptureDCR-7-3 upper

DCR-2Joint region yielding

teel casing buckling

Stee

DCR-6 lowerGusset plate bucklingGusset to beam, von Mises yield criterion

DCR-7-1 lowerp g, y

DCR-7-2 lowerGusset to beam, tensile rupture

Gusset to beam, shear ruptureDCR-7-3 lower Diagonal configuration - 21 DCRs

Design checks of chevron BRBFDesign checks of chevron BRBF

DCR-3 right upperJ i t gi b kli g

DCR-3 left upperJoint region buckling

7 Categories of limit state

Joint region bucklingg g

DCR-4 leftGusset plate block shear failure

DCR-4 rightGusset plate block shear failure

DCR-5 left upperGusset plate yielding

DCR-5 right upperGusset plate yielding

ng buckling Steel casi

Gusset plate block shear failure Gusset plate block shear failure

Steel casing sing buckling

Gusset plate yieldingDCR-5 left lower DCR-5 right lower

Gusset plate yielding

DCR-3 left lowerJoint region buckling

DCR-3 right lowerJoint region buckling

Chevron configuration - 33 DCRs

Brace On DemandBrace On Demand browser browser Brace On DemandBrace On Demand browser browser Design requirement

space strength stiffnessspace strength stiffness

Design results

1 WES-BRB1.WES-BRB2.Gusset 3 Welding3.Welding4.DCR checks

http://bod.ncree.org.tw

User guide for BOD usersUser guide for BOD usershttp://bod.ncree.org.tw

DemanCa

=p

DCR dacity

7 categories of limit state Load and Resistance Factor

Capacity

Load and Resistance Factor Design

Specification for Structural Steel pBuildings (AISC 360-10)

Seismic Provision for Structural Steel Buildings (AISC 341-10)

P.C. Lin, K.C. Tsai, K.J. Wang, Y.J. Yu, C.Y. Wei, A.C. Wu, C.Y. Tsai, C.H. Lin, J.C. Chen, A.H. Shellenberg, S.A.Mahin C W Roeder Seismic design and hybrid tests of a full-scale three-story buckling-restrained frameMahin, C.W. Roeder, Seismic design and hybrid tests of a full-scale three-story buckling-restrained frameusing welded end connections and thin profile, Earthquake and Structural Dynamics, 2012, 41:1001-1020P.C. Lin, K.C. Tsai, A.C. Wu and M.C. Chuang, Seismic design and test of gusset connections for buckling-restrained braced frames, Earthquake Engineering and Structural Dynamics, 2013, eqe. 2360

ConclusionsConclusions1.1. The effects of The effects of BRB axial forceBRB axial force and and frame action frame action

must be considered to compute the demands for must be considered to compute the demands for BRB component and gusset plate design.BRB component and gusset plate design.

22 TheThe GUFMGUFM and theand the equivalent strut modelequivalent strut model areare2.2. The The GUFMGUFM and the and the equivalent strut model equivalent strut model are are adopted for BRB axial force and the frame action adopted for BRB axial force and the frame action effectseffectseffects.effects.

3.3. The BRBF tests and FEM analysis showed the The BRBF tests and FEM analysis showed the proposed method can be used to evaluate the proposed method can be used to evaluate the gusset interface forces.gusset interface forces.

4.4. The beam with suitable flexural capacity is The beam with suitable flexural capacity is suggested since it lowers the frame action forcesuggested since it lowers the frame action forcesuggested since it lowers the frame action force suggested since it lowers the frame action force demands on gusset plate design.demands on gusset plate design.

Thanks for your attentionThanks for your attentionThanks for your attentionThanks for your attention